Synchronizing system



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Patented Apr. 16, 1946 SYNCHRONIZING SYSTEM Maurice Artzt, Haddonileld, N. J., asslgnor to Badio Corporation of America, a corporation of Delaware Application April 17, 1942, Serial No. l439,343

' 12 claims.

My invention in general relates to apparatus for synchronizing the operation of two prime movers, and more particularly to synchronizing apparatus for operating co-phasally the driving motors of the scanner and receiver in a facsimile system. 1

At the present time there are a number of different synchronizing methods, arrangements and apparatuses which have been suggested for the purpose of synchronizing the operation of the drivingmotors for a facsimile transmitter and receiver. These, however, suffer severe disadvantage in that theyfare practically unadaptable for use when the facsimile transmission is accomplished at comparatively high speeds. Accordingly, it is one of the objects of my invention to provide apparatus for synchronizing the operation of such motors when transmissionand reception of facsimile material is accomplished at what, at the present time, is considered to be very high speeds.

It will be appreciated that since this transmission takes place'at comparatively high speeds, any synchronizing devices not only must be able to accomplish synchronization but such synchronization must take place within a very short ofthe objects of my invention to provide an arrangement whose corrective influence is accomplished substantially without inertia.

At the present time the art of facsimile is iinding considerable vapplication with the military forces, since such materialsgas orders, maps, and lthe like-may be sent and compared with known material for the purpose of avoiding the reception of misleading or fraudulent orders. 1 The devices must be as simple as possible and as rugged as possible due to the difllcult conditions under which they are operated.' Accordingly, it is another of the objects of my invention to provide a synchronizing arrangement of the type hereinbefore referred to which will be lparticularly adaptable for military purposes.

My .invention in general contemplates the transmitting of a synchronizing signal, comprising a plurality of cycles of a wave formation, from the transmission apparatus at the end'of leach line scanned by a facsimile scanning apparatus. At the receiver there is furnished a motor which is adapted to run with a speed which bears a direct relationship to the frequency of the power supplied to it. A vibrator arrangement is sup- Accordingly, it is another of the objectsof my invention to provide apparatus of the type hereinafter to be described which will be accurate and positive in action and will accomplish synchronization in a minimum amount of time when such apparatus is operating non-synchronously.

It has been suggested heretofore the idea of utilizing synchronizing pulses comprising a set of comparatively high frequency pulses which are transmitted for a deilnite interval of time. Heretofore the devices which utilized the synchronizing signals had the action thereof either slowed down or defeated for a period of time because of receipt and comparison of these pulses with locally generated pulses after an interval had passed. Accordingly, it is another'of the objects of my invention -to provide a device which will act or be effective to accomplishl this desired result, regardless of the time of receipt of the synchronizing pulses. i

Also amongfthe disadvantages of the apparatuses according to the' prior artv there has been the fact that considerable slowing up of correction has taken place due to the inertia of the deplied which develops pulses of afrequency bearlng a relationship tothe frequency with which itis driven. The vibrator is energized or driven by the output of an oscillator which is oscillating at a particular'frequency, in this case, 60 cycles. The arrangement is such that there should normally be produced six cycles of the 60-cycle energizing oscillation between line synchronizing signals. At the receiver the line synchronizing signals may be divided out or separated from the picture signals due to the particular frequency which comprises the line 'synchronizing signal. After the separation has taken place, the signal may be. rectified to give substantially a singlel pulse, and if the machines operate in synchronism the beginning of this single pulse occurs at the same instant as the beginning of one of the cycles vlces'whichvaccomplished the correction when `non-synchronous operation was taking place.

This, of course,`is undesirable particularly in high produced by the 60cycle oscillator, and hence no action takes place to disturb the receiver. However, if the line synchronizing signal ds not occur simultaneously with one of the cycles of the 60-cycle oscillator, the line synchronizingl signal will immediately pull the oscillator to' its own beginning point so that the oscillator itself is'.

definitely controlled by the line synchronizing signal and is done so in an yinertialess fashion. There is provided also a commutating -arrangement associated with the motor, which assures the factthat the curve Signal will act only on the correct half-cycle of the oscillator of the 60-cycle oscillating note generated, so that any correction will be accomplished simultaneously and definitely and positively.

My invention will best be understood by reference to the drawings, in which:

Figs. l and 2 are explanatory curves.

Fig. 3 shows an arrangement for controlling an oscillator output in accordance with my invention.

Fig. 4 is a schematic showing of an embodiment of my invention.

Referring to Fig. 1, there is shown an explanatory curve which illustrates the normal synchronizing operation of the facsimile transmitter and receiver in accordance with the contemplation of my invention. For purposes of convenience, the synchronizing signal is illustrated as being a square pulse, although, as a matter oLfact, the received synchronizing signal is put through a distorting network which changes its wave shape so that if the occurrence of the signal is simultaneous with that of a note from the 60 cycle oscillator, the two wave shapes should coincide both in occurrence and in shape. Referring to this figure, the synchronizing signal ill is illustrated as occurring at the same instant as a part of the note from the 60 cycle oscillator, and this portion is illustrated as the positive half of the cycle. Between synchronizingvsignals there occur six cycles of power supplied and the next synchronizing signal occurs after the generation of these pulses.

Referring to Fig. 2, there is mustreted the feet that the synchronizing signal is transmitted as a burst of oscillations having a frequency of sub` stantially four kilocycles, and the picture signals are illustrated merely by showing a seven kc. signal carrier, and this illustration shows the two as being of diiering amplitude. It will be appreciated that separation of the synchronizing signals from the seven kc. signal carrier may be done by well known means and may be done in a comparatively easy manner.

Referring to Fig. 3, there is shown an oscillator and its control for obtaining synchronism in an arrangement according to my invention. Referring to this figure, the four kc. synchronizing signal is impressed onto the primary 20 of a transformer having a secondary 2| across which is connected a condenser 22, thus peaking the transformer at a four kc. peak. The secondary i is connected across the anodes 23 and 24 of a full wave rectifier 25. The output of the full wave rectifier is connected through a resistor 2B and a threshold biasing source 21 and across the control grid-cathode path of a therrnionic tube 28. Also connected across the control grid-cathode path of this tube are two serially connected time constant circuits comprising condensers 30 and 3|. and resistors 32 and 33. Connected to the terminal of resistor 26, which is uncommon to the time constant circuits and connected to the common terminal of the time constant circuits is a switching arrangement which is indicated by a legend.

'I'here is'provided an oscillator which cornprises a thermionic tube 40 which, in this illustration, has anode, cathode, control grid, screen grid and suppressor grid electrodes. The cathode of this tube is connected through a resistancecondenser combination comprising a resistor Il and condenser 42 to ground. The screen grid thereof is connected back to the anode thereof tively long time constant.

through a resistor 43, and is also directly connected to the anode of a thermionic tube 44 having three electrodes in this illustration. The anode of the tube I0 is connected directly to the control electrode of the tube 44 and the cathode of the' tube 44 is connected to ground through resistor 45. Connected between the cathode of the tube 44 and the control electrode of tube 40 is a series of resistance-condenser combinations which determine frequency of oscillation of the device as an oscillator.

The resistances and condensers are those identified in the drawings as 50 through 51. The anode of tube 28 is tied to the common terminal of condenser 52 and resistor 56 by conductor 5l. The anodes of tubes l0 and M and the anode oi tube 2B are energized by a supply. (not shown) identified as +B, the negative side thereof not being shown and 'being grounded. The supply connects to the anode of tube 28 through variable resistor 59.

The action of the device is as follows. The tubes 40 and M and the network of resistances and condensers along with tube 28 and with its output resistance, comprise an oscillator set normally for 60 cycles. The tube 44 furnishes an impedance step down from the plate of tube 4I to the resistance capacity network. The tube 28 is normally at zero bias and under this condition the frequency of oscillation is 60 cycles. If the tube 28 is biased to cut off, the shunting impedance across the resistor 58 becomes higher and the network will then cause oscillations of a frequency lower than 60 cycles.

Normally, if the device is operating in synchronism with the transmitter, the synchronizing pulse will arrive and be rectified by the rectier having anodes 23 and 24 and will cause tube 28 to conduct by overcoming the comparatively high threshold bias 21. This will affect the circuit comprising condenser 30 and resistance 32 which has a comparatively short time constant, and condenser 3| and resistance 33 having a compara- This rectified synchronizing signal will be in phase with the beginning of a cycle of the oscillator and there will be no effect, then, in so far as the synchronizing signal is concerned, the synchronizing signal being reshaped to be approximately a sine wave by the action of the time constant circuits in the grid-cathode branch of tube 28. The action of the synchronizing signal, if it arrives slightly ahead of the normal oscillation of the oscillator, will be merely to initiate the oscillation or pull the oscillator into step with it.

On the other hand, if the synchronizing signal should arrive when there is a too great disparity between the signal and the oscillator, the socalled frame commutator, or switch, will be in a closed position and will short out resistance 28.

and condenser 30 and resistor 32, and the synchronizing signal will charge the time constant circuit comprising "resistor 3| and condenser 33 to a fairly high value. Whereas, when the condition existed that the commutator was open when the synchronizing signal camein, most oi the voltage drop wasacross resistance 26 and resistance-condenser combination 30, 32, now the full voltage is impressed across condenser 3| and resistance 33, and this will drivethe terminal of resistance 33 connectedto the grid of tube 28 negative and hold it there for a comparatively long time because of the time constant of condenser 3| and resistance v33. This means tube 28 is blocked or cut of! and the shunt impedance across resistance 58 is increased and the oscillawr will oscillate at a natural frequency lower than 60 cycles. Due to the fact that in a comparatively short time the framing commutator will be open at the time the synchronizing signal arrives, the synchronizing signal will then take over to initiate 'and control oscillation. In actual practice this has been found to be a very rapid acting arrangement and synchronism is restored in a minimum interval of time. The oscillator is used toenergize the driving winding of a vibrator arrangement which interrupts a direct current. The vibrator then will interrupt the current in accordance with the frequency of the current supplied to the windings thereof. 'I'he motor for ondary of which is connected to the anodes of the driving the recorder is of the induction synchronous type, and will be driven in accordance with the frequency of the current supplied to it. The

result then is that without the use of any en gaged or slipping clutches, the motor may be driven directly and positively. The action on the driving motor will be discussed more fully herein' after.

Referring to Fig. 4, there is shown schematically an embodiment of my invention with the appurtenant apparatus actually used in the arrangement as built. A twin power supply is used to give a 400 volt supply above ground for the printer section output, and a 150 volt supply below ground is developed for the amplifier and control system.

The normal 110 volt 60 cycle power supply passes upon the closing of switch 60 to transformers 6| and 52, respectively. Transformer 6| is a multiple secondary transformer. Energy is impressed onto full wave rectifier 63 and the output thereof passes to the printer output stage comprising thermionic tube 64 and the associated output circuit thereof. A single filter capacitor 65 is connected in the anode-ground circuit of the tube. The half wave rectifier 68 provides a. source of direct current 150 volts below ground. This supply is carefully filtered by means of tapped resistor 81 with theassociated filter capacitors 68, 89, and 1|. Also connected across this source of filtered direct current supply is a regulating tube 12. 'I'he source ls then connected to a resistor potentiometer arrangement 13 having a condenser 14 shunted across a part thereof and a potentiometer arrangement shunted across another part thereof. A condenser 16 is connected between one terminal of resistor 14 and the sliding arm of the potentiometer 15.

The input of the composite picture and synchronizlng signal received from a facsimile transmitter and impressed onto the receiver is indicated by the jack 80. This is impressed onto a condenser 8| connected in selles with a resistor 92, the latter being connected to a cathode resistor 83 at the terminal thereof remote from its connection with the cathode of thermionic amplifying tube 84. The anode of tube 84 is grounded through resistor 85. Theanode of tube 84 also connects through a condenser 86 to the grid of a thermionic tube 81 by Way of resistor 88. The functionof tube 81 will be explained hereinafter. The anode of tube 84 also connects through condenser 86 to the ygrid of a thermionic tube 89 by Way of resistor 90. A grid-cathode resistor 9| is provided connecting between the grid of tube 89 and one terminal of cathode resistor 92. The latter resistor is connected through a cathode resistor 93 to the cathode of thermionic tube- 94, whose function will be explained more fully hereinafter. The anode of tube 89 is grounded chronizing signal.

double diode section of` a duo diode trlode thermionic tube 95.

The center tap of the secondary of transformer 93 is connected directly to the grid of the tube96 and the grid in turn is connected through a time constant` circuit 91 comprising a resistance and a condenser, each connected in parallel with the other to the cathode `of tube 96. The anode of tube 98 is connected to the grid oftube 94 and the grid lin turn is returned to the cathode through a resistor 98. The cathode of tube 84, which is the output tube, then is connected to one electrode of the recorder, the other electrode comprising the recording drum per se which. is

grounded at 89.

Tube 94 has connected in the output circuit thereof a tuned transformer |00 which is tuned to give a peak response at 4,000 cycles, which is the frequency of the pulses forming each syn- The secondary of this transformer is impressed onto a full wave rectifying tube |0|, and the center tap of the secondary of the transformer is connected back to the cathode of the tube through condenser- |02, and is also connected directly to a control grid of tube |03 through resistor |04. The control grid of tube |03 is connected back'to the cathode of the tube through two time' constant circuits comprising condensers |05:l and |06 havingresistors |01 and |08 respectively connected substantially in par- -The common terminal between resistor ||2 and condenser ||1 is connected to the anode of tube |03 through resistor I8, this anode being grounded through the variable resistor arrangementl I9.

The primary of tuned transformer |00 also is directly connected to the anode of a thermionic tube |20, the anode being grounded. 'I'he control electrode of tube v| 20 is connected directly to the anode of a thermionic tube |2|, and the anode of this tube-is grounded through resistor |22. The screen grid also is connected to ground. The cathode of tube |2| is connected through a time constant circuit comprising resistor |23 and condenser |24 to the'common terminal of resistors |09 through ||3 and the common terminal of these resistors also is connected back to the cathode of tube 81 through resistor |25 and to the anode of tube 81 through resistor |26 and condenser |21, the anode of this tube being directly The anode of rectly to the control grid of tube 94 which has the tuned transformer |00 connected in the output thereof. f

The cathode of tube |20 is connected to the common terminal of resistance |09 and condenser H4, and this common terminal is connected through condenser |30 and resistance |3| to the portion of the power supply potentiometer where condenser 14 connects into the active part of the potentiometer. Also, this cathode is connected through condenser |30 and resistance |32 to the of tube |20 also is connected through condenser |30 and resistance |40 to the control electrode of a thermionic tube |4| which has the cathode thereof grounded. The anode of this tube con- .nects to the driving coil |45 of a make and break double contact; vibrator unit having amature |46 and contacts |41 and |48. These contacts are connected to the armature and to each other through condensers |49 and |50. Shunted directly across the contacts is the primary |5| of a transformer having a tapped secondary |52, the secondary having connected thereacross a condenser |53. Each side of the secondary is grounded through a condenser, these condensers being condensers |54 and |55. 'I'he secondary |52 is connected across one winding of the motor |35, and this arrangement consists in a conductor |60 running from one side of the secondary directly to the common terminal of the twp windings of the motor illustrated and a conductor |6| which runs to a common terminal of a pair of condensers |62 and |63 connected in parallel with each other, one common terminal thereof being connected to the uncommon terminal of one of the windings of the motor, and the other common terminal thereof being connected to the uncommon terminal of the other of the windings of said motor.

The center tap of the primary |5| is connected to one terminal of winding |45, and also to the terminal of filter choke |10, the other terminal of filter choke |10 being connected to the center tap of a secondary winding |1|, and being grounded through a condenser |12, the grounded terminal of said condenser being connected to the center tap of secondary |13.

'I'he terminal of filter choke |10 which is common with the center tap of primary |5| is -grounded through by-pass condenser |14. The secondary |13 is connected directly across theplates of a full wave rectifier |15.

The driving motor shaft is connected to the shaft of the recording drum |80 through appropriate gears |8| and |82. Also connected on this shaft is a make and break cam |83 which makes and breaks the circuit between a pair of conductors |84 and |85, one conductor being connected to the commonterminal of the time constant circuits including condensers |05 and |06, and the other conductor being connected to the terminal of resistor |04 which ls common with the center tap of transformer |00.

The action of the device is as follows:

A twin power supply system has been provided in the actual apparatus which gives a 150 volt supply below ground for the amplifier and the control system, and a 400 volt supply above ground for the printer output. Both of these have been obtained by using the rectifier 63 for the 400 volts above ground and the rectifier 66 for the 150 volts below ground. The 400 volt supply has utilized only one filter capacitor 65 and supplies only the printer output stage utilizing the tube 64. On the other hand, the 150 volt supply is carefully filtered by means of the tapped resistor 61 and the capacitors 68, 69, 10 and 1|. The voltage is regulated by means of the regulator tube 12 and the bleeder 13 provides two additional voltage taps filtered by condensers 16 and 14.

All filaments of the various tubes have beenA a'soacss art. One side of the supply is grounded. 'Ihe printer output stage utilizing the output tube 64 has the recorder printer as a cathode load so that the voltage supplied to the printer bar 20| is always positive'with respect to ground. The grid resistor 98 of this tube is returned to cathode so that if no grid excitation is provided the tube 64 will be at zero bias and draw current through the printer and print a maximum of color. However, since this same grid resistor is the plate resistor of the triode section of tube 96, which `is at zero bias, suiiicient current through this resistor is passed to hold tube 64 at cut off.

. A two stage signal amplifier, includingV the tubes 84 and 89, is provided for amplifying the incoming tone and impressing it onto the primary of transformer 93. The output tone from this transformer is rectified by the duo diode sec tion of tube 96 and this then appears as a negative bias on the grid of the tube. Thus, when the tone level is high enough, the triode section of tube 96 will be cut off, and will allow the tube 64 to pour a full output current into the printer. Intervening values of tone will drive the triode section of tube 86 partially to cut ofi and thus intervening values of printing current will be delivered by the tube 64 to the bar 20| and drum |80. Thus the output current of tube 64 is proportional to the tone level fed into the duo diode section of the tube 96. The volume control at the input to tube 84 is regulated to give the necessary signal for the depth of color desired, and hence regulating this volume will lighten or darken the received picture.

While only a portion of the signal in the output circuit of tube 84 is passed on to the tube 89 for the printer, all of its output is passed on to tubes 81 and 94. These two tubes have series grid resistors 88 and |29 to make saturation easy, so that the output of tube 94 will1 be a square wave when the volume is set to give proper printing. Changes in signal level on the input then will aiect the output of tube 94 but very little, as this amplifier acts as a limiter. The output of tube 94 is tuned into the transformer |00 and the tuning peak is set at 4,000 cycles. Thus, only the phasing signal, which is of a frequency of 4,000 cycles, will produce full output from the transformer, and all picture signals, which are in the neighborhood of 7,000 cycles, and interference and the like, will be at a much lower level. Hence, the synchronizing signal has been separated from the composite input sig? nal. The 4,000 cycle synchronizing signal is then rectified by the full wave rectifying tube |0| and this tube is set with a bias of greater Value than the undesired signals can ever attain in the transformer |00. The output of tube 0| feeds into the network comprising resistors |04, |01 and |08 and condensers |02, |05 and |06. The values of these constants are so set that the signal voltage across condenser |06 and resistor |08 is normally very small and almost all of the voltage appears across resistors |04 and 01. This will be a uni-directional pulse with a slope rounded by capacitors |02 and |05 and which corresponds approximately to the slope of a 60 cycle. sine wave.

rihe tube |2| and the network comprising resistors |09, ||0, ||2 and ||3, and condensers ||4, |I'5, ||6, and ||1 comprise a phase shift oscillator set normally for 60 cycle output. To enable the tube |2| to properly drive the low impedance network for this frequency the cathode follower tube |20 is used to furnish an impedance step down from the plate of tube I 2| tothe network. In this network'the resistor il! has an additional parallel path to ground in the tube |08 through resistor lll. This tube then is shunted to ground (+B for this tube) by the resistors comprising the unit H9.

The tube |03 is set normally at zero bias and under this condition the frequency of the oscillatoi is adjusted to 60 cycles by the variable control of resistance unit |I9. If the tube |03 is biased to cut off the shunting impedances across resistor H2 become higher and thus the network is set for an output from the oscillator of a frequency lower than 60 cycles, and in actual operation about 55 cycles. a

In normal operation the synchronizing or phasing pulse will be very short in duration and will comprise about one half cycle of a 60 cycle note, and this is fed to the tube |03 at a low level from the resistor |01. This pulsing of the oscillator network will tend to lock the oscillator'into synchronism with the pulses. In actual operation the phasing pulses from the scanner occur ten times per second, or once per scanning line. Therefore, the oscillator will receive a locking pulse once every 6 cycles of its 60 cycle output, and accordingly very accurate control of this 60 cycle frequency is obtained by this method of pulsing.

The output of the 60 cycle oscillator is irnpressed upon the grid of the tube lli, and the The above described phasing and .locking will occur only if the motor happens to be locked on the vibrator in the correct polarity, that is, with the rotor in the correct position upon receipt of the positive half of the cycle of the vibrator o utput. As explained before, it is possible for the motor to be 180 out from this position electrically, and for this reason asecond commutator is 'fadded on the motor shaft and has two conducting and two non-conducting positions corresponding to the plus and minus halves of the frequency supplying the motor. This commutator connects into the grid of tube IM which drives the vibraoutput of this tube actuates the driving coil of a vibrator which keys the direct current lpower supply which is the output of tube |15, and since the armature of the vibrator will follow the frequency of the driving current, the power output of the vibrator will be an accurate 60 cycles if an accurate 60 cycles is impressed onto the driving coil.v

As the recorder driving motor is of the induction, synchronous type, it can lock into synchronism with its supply on either half of the cycle, and since approximately 6 cycles occur between synchronizing pulses, there are, therefore, twelve possible'places for the recorder motor to lock into synchronism with' the output of the oscillator. As only one of these twelve possible places is the correct framing position, a system of commutators is used to make sure that the lock can occur only at the correct place. The main phasing commutator on the recorder drum shaft consists of a contacior that normally is closed during the entire scanning line, and open only during the-time that a. phasing pulse is sup- DOSed to be received. This pair of contacts is connected across the two conducting members |84 and |85. If the synchronizing signal is received at the correctV time the tube il'receives the usual short pulses to lock the oscillator in synchronism. If these pulses come in at the wrongtime they will come in when the phase contacts are closed, these being closed during an actual scanning line and openduring the time a pulse is normally received, and thus the resistor |08 and capacitor |08 are connected directly across the output of the rectiiler. The time constant of resistor |08 and condenser |08 is very vlong and this combination will charge rapidly, but

discharge very slowly. Thus, the voltage; across the grid of tube |03 no longer consists of short pulses, but almost of a steady negative voltage sumcient to change the frequency of the oscillator to a value lower than 60 cycles.

The recorder motor, which now will' be slow..

and without locking control, will drift rapidly untor, and changes the lbias ofthis tube as well as the grid resistance III by paralleling resistor |32 across it. The tube III normally is biased below cut of! so that only the positive half cycles from 'the oscillator make it draw current and excite the vibrator. When the motor is properly locked in the correct polarity the commutator will decrease the negative bias of tube |4| when it gets a positive half cycle, and increase its negative bias when the negative half cycle appears, and thus they work together. If the motor is 180 out of phase with the positive half cycle of the supplied lenergy the commutator and the oscillator feed to the grid of tube ill are in opposition and the vibrator is driven much less positively. lube HI then no longer goes completely to cut off and the vibrator will tend to hold closed on one side of the cycle. This'causes the motor to receive much less power and it drops out of synchronism with the vibrator. As soon as it losesthe motor will be locked into synchronism only when it is in the correct phase yposition to hold true synchronism, and at all other of the twelve possible phase. positions it will be unstable and drift rapidly into the correct phase. Phasing, therefore,L is very fast and exact.

Should the composite signal which normally is received fade out then no synchronizing or other signals will be received by the tube N3 to change vthe oscillatorgfrequency, orto lock it into correct phase so that the oscillator will run at its normal frequency until pulses again are restored. As the resistor-condenser type of oscillator is very stable with changes in line voltage and the like, this drift is very small and synchronism is usually re-established immediately with the first pulse received. For instance, when the device is first Vstarted the recorder will phase and lock in usually the direct current voltage into a cycle alter-v vhating current with frequency controlled by the 4vibratorl armature. This vibrator is not operated as a self-excited unit, but receives its operating pulses from the tube lll. Thus the frequency is determined by the oscillator and the synchronizing system which determine when pulses will be fed to the driving winding of the vibrator, and not by the natural period of the vibrator. The plate supply voltage of tube lli may be obtained from the rectified output of the tube |15.

It should be understood that the contempla.- tion of this invention includes not only the synchronizing of motors which are located at a oonsiderable distance apart, but also separated motors which are located close together as, for instance, a device could be used in the same building, or in the same room, for synchronizing two motors as if the motors were located considerable distances apart, and the terminology from which will remain within the spirit and scope of the invention, and I claim all such departures as fall fairly within the spirit and scope of the hereinafter appended claims.

What I claim is:

1. Apparatus driving a local motor in synchronous relationship with a remote motor and wherein signals representative of the speed and phase of the remote motor are received at recurring intervals, comprising a local motor, oscillating means for producing electrical waves, commutatlng means. means associated with said oscillating means for changing the frequency of said oscillating means in accordance with the conductive state thereof, means for impressing said recurring signals onto said latter means whereby the conductive state of said latter means is governed in accordance with the position of said commutating means, energy supply means governed by said oscillating means, and means for impressing the governed energy supply onto said local motor.

2. Apparatus in accordance with claim l, wherein the means for changing the frequency of the oscillating means in accordance with the conductive state. thereof includes a thermionlc tube.

3. Apparatus for synchronizing the operation of a remote and local electric motor wherein a recurring synchronizing signal indicative of the v speed and phase relationship of the remote motor is received, comprising a local motor, oscillating means, thermionic tube means connected to said oscillating means, said thermlonic tube aifecting the frequency of said oscillator in accordance with the conductive state thereof by controlling the impedance connected'in the frequency determining circuit of said oscillator, means for impressing impulses representative of the recurring synchronizing impulses onto the gridcathode path of said tube, commutating means mote electric motor, comprising oscillating energy developing means, means for affecting the frequency and phase of said oscillating energy means in accordance with the time of receipt of the received signal indicative of the phase and Speed of the remote electric motor, means for impressing said energy upon the local motor to be operated in synchronous relationship with the said remote motor, and commutating means connected to the local motor for determining which cycle of the operating energy of said motor is affected by the received recurring signals to affect the phase of the developed oscillating energy.

5. In a lsynchronizing system for synchronizing the operation oi*J a local and a remote electric motor, and wherein recurring signals are received which are indicative of the speed and phase of the remote motor comprising a local motor, means for energizing the local motor by a variable wave whose phase may be affected by said recurring signals, commutating means operated by said local motor for determining which cycle of the variable wave is affected in phase by the received recurring signals.

6. Apparatus in accordance with claim 3, comprising, in addition, a wave shaping circuit connected in the grid-cathode path of said thermionic tube, and means for impressing on said circuit signals representative of the recurring synchronizing signal.

7. Apparatus in accordance with claim 3, comprising, in addition, s, wave shaping circuit connected in the grid-cathode path of said thermionic tube, and means for impressing signals representative of the recurring synchronizing signal on said circuit, and wherein said commutating means connected in the grid-cathode path of the thermionic tube is connected across at least a portion of said wave shaping circuit.

8. Apparatus for synchronizing the operation of a local electric motor with a remote electric motor and wherein a recurring synchronizing signal is received which is indicative of the speed and phase relationship of the remote motor, com- Drislng a local motor, oscillating means, thermif onic tube means connected to said oscillating means, said thermionic tube aifecting the frequency of said oscillator in accordance with the conductive state thereof by controlling the im pedance characteristics of the frequency determining circuit of said oscillator, wave shaping circuit means connected in the grid-cathode Path of said tube, said wave shaping circuit comprising resistive and condenser means, means for impressing impulses representative of the recurring synchronizing impulses onto a grid-cathode path of said tube, commutating means driven by said local motor and connected in the grid-cathode path of said thermionic tube for influencing the eil'ectof said synchronizing pulses on said thermionic tube, energy supply means controlled by said oscillating means, and means for impressing said energy supply onto said local motor.

connected in the grid-cathode path of said 55 9. Apparatus in accordance with claim 8,

thermionic tube and aifecting the effect of said recurring impulses on said thermionic tube, energy supply means under the control of said oscillating means, and means for impressing said energy supply onto said local motor.

4. Apparatus for maintaining at least one local electricmotor in synchronous rotative relationship with a remote electric motor and wherein an electrical signal is received at recurring interwherein there is provided in addition means for separating the synchronizing pulses from the remainder of the received signal and means for rectifying said synchronizing pulses, and means vals to indicate the speed and phase of the re 1| commutating means associated with said oscillating means whereby the cycle .of oscillation of said oscillating means, whose phase is affected, is predetermined.

11. Apparatus in accordance with claim 3, wherein said energy supply means under the control of said oscillating means comprises a vibrator switching unit having the driving coil for the vibrating portion thereof energized entirely by said oscillator.

` l2. Apparatus for maintaining at least one local electric motor in synchronous rotative relationship with a remote electric motor, comprising a source of signal energy produced at recurring in tervals to indicate the speed and phase of the remote electric motor, a local motor, oscillating energy developing means including an oscillator having a predeterminable frequency, means for affecting the frequency and phase of said oscillating energy developing means in accordance with the time of receipt of the said signal energy indicative of the phase and speed of the said re- 'mote electric motor, means for impressing said 15 vals.

MAURICE ARrrz'r.l 

